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| Shipwrecks on Sanctuary Shores: Disturbance and Recovery Along a Rocky Intertidal Exposure Gradient |
Principal Investigator(s)
Laurie McConni (Moss Landing Marine Laboratories, California State University)
Mike Foster (Moss Landing Marine Laboratories, California State University)
Andrew DeVogelaere (Monterey Bay National Marine Sanctuary)
Ron Walder (Moss Landing Marine Laboratories, California State University)
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Start Date
1996-04-01
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Funding
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Overview
Recovery rates and processes were assessed along a rocky intertidal exposure gradient impacted by a shipwreck in Monterey Bay, California. This anthropogenic disturbance was used to determine if recovery rates varied inversely with tidal height due to reduced abiotic stress. Disturbed and control (undisturbed) plots were established in a mid/high intertidal red algal (dominated by Endocladia muricata and Mastocarpus papillatus), mid intertidal mussel (Mytilus californianus), and low intertidal surfgrass (Phyllospadix torreyi) assemblage.
Percent cover of sessile organisms in 0.25 x 0.25-m plots in each of the assemblages was assessed between 1996-1998 and 2001-2002.
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Summary to Date
Results indicated recovery was variable over the exposure gradient. Ephemeral seaweeds initially colonized all disturbed plots, but were replaced by later successional species within 2-12 months.
Recovery rates did not vary inversely with tidal height as expected. Instead, relative recovery was greatest in the high intertidal red algal assemblage, followed by the surfgrass and Mytilus assemblages.
The patterns of recovery suggest that assemblages characterized by a few dominant species that recruit rapidly and grow quickly will recover faster than those dominated by organisms with variable, episodic recruitment, or those that have limited success with sexual reproduction relative to vegetative propagation. This study highlights the importance of species’ life history to recovery after disturbance, and the inability of current ecological models to accurately predict successional pathways and community development on rocky intertidal shores.
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Monitoring Trends
- High intertidal red algal assemblages recovered most rapidly (less than 3years). This recovery is attributed to early re-colonization of Mastocarpus papillatus and Endocladia muricata.
- Low intertidal surfgrass assemblages have not recovered 6 years after the initial disturbance, but appear to be recovering more rapidly than mid intertidal Mytilus assemblages. Presumably seed production, and seedling mortality contributed to the delayed recruitment of Phyllospadix and reduced recovery within this assemblage at Pt. Pinos as well as slow re-colonization of invertebrates.
- Mytilus assemblages have been the slowest to recover (more than 6years) and have yet to reach abundances similar to those observed in natural stands. Most recruitment has been from plots edges and suggests that re-colonization up until now has not been from new recruitment, but was instead from individuals creeping in from surrounding areas.
- Recovery does not vary inversely along an intertidal exposure gradient. Instead, recovery appears to be related to varying complexity in species life histories that characterize each assemblage.
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Discussion
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Study Parameters
Click here to view the parameters measured in this study. |
Study Methods
Click here to view the methods and materials used in this study. |
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Images and Documents
Grounded ship, the F/V Trinity being rolled to shore in the salvage operation.
F/V Trinity on the rocks, just north of Pt Pinos.
Healthy mussel bed. An undisturbed, healthy 25 x 25 cm control plot.
In a mussel bed, after six years of recovering from the vessel grounding.
A 25 x 25 cm area of healthy seagrass, Phyllospadix.
A seagrass area after six years of recovery from the vessel grounding.
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